New research links contraceptive pills to an increased rate of prostate cancer. Don't worry: you haven't been taking it wrong all these years. There's a body of research that links prostate cancer to increased exposure to estrogen, and it's possible that widespread use of the Pill could cause an uptick of the hormone in the environment. The logic is that the estrogen is passed into the sewage system through urine, where it makes its way into the water cycle and the food chain. From there people are exposed to it, and hence the problem.

The research (available to read in full) looked at the rates of oral contraceptive pill use by country, and found a strong correlation with the rate of prostate cancer — but they're quick to label it as not definitive:

This study represents the first systematic analysis of associations between OC use and prostate cancer. It is an ecological study and thus has, as with all correlational studies, significant limitations with respect to causal inference. As such, it must be considered hypothesis generating.

While there is some evidence that hormones have made their way into the water supply, there isn't any proof that it's in high enough concentrations to affect animals or people. Hopefully further research will definitively show if there is a link between the two.